I am 62 y.o. post-menopausal female. For the last 3 yrs. I have been on Estradiol 1 mg 21 days on and 7 days off. After 9 yrs of NO periods, I recently had a period that was extremely painful and lasted 5 days with moderate bleeding, including passing a blood clot. My GYN said, after the vaginal ultrasound, that I have a thickened uterus. What are my chances that these latest symptoms are due to the Estradiol,,,or might be uterine cancer. There is no female type cancer in my family history.